Image reader having electrical and optical means for varying magnification

ABSTRACT

An optical image reader having the capacity to vary magnification both electrically and optically is provided. Operator controls permit variable magnification of image signals to a desired level. An optical sensor can be independently moved for focusing.

This is a division of application Ser. No. 607,858, filed on Oct. 30,1990now U.S. Pat. No. 5,097,519, which is a continuation of U.S. Ser.No. 173,986, filed on Mar. 28, 1988, now abandoned, which is acontinuation of U.S. Ser. No. 865,894, filed on May 21, 1986, and issuedas U.S. Pat. No. 4,771,473 on Sep. 13, 1988.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus which can read a documentat a desirable magnification.

2. Description of the Prior Art

In an image reader, the density of a document is read with an imagesensor and is sent to an external output apparatus such as a printerafter being transformed into bi-level data.

In a conventional image reader, the magnification for reading is variedby processing signals electrically.

In the electrical variation of magnification, image signals from theimage sensor are processed electrically so as to enlarge or reduce theimage, while the resolution of reading by the image sensor is keptunchanged.

An essential disadvantage in the electrical variation is that an outputimage is made coarse upon enlarging the image at high magnificationbecause it is enlarged without heightening the resolution of reading.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image reader whichcan read an image and maintain resolution even at a highermagnification.

Another object of the present invention is to provide an image reader inwhich the magnification of reading can be varied over a wide range.

A further object of the present invention is to provide an image readerin which an image can be enlarged or reduced optically.

A still further object of the present invention is to provide an imagereader in which an image can be enlarged or reduced according to theresolution of a printer connected to the image reader.

According to the present invention there is provided an image reader forreading an image of a document, comprising: (1) an optical projectionmeans for projecting an image of a document; (2) an image reading meansfor transforming the projected image into electrical image signals; (3)a first variable magnification means for varying optically the size ofthe image to be projected on the image reading means; (4) a secondvariable magnification means for varying electrically the size of theimage projected on the image reading means by transforming theelectrical image signals received from the image reading means intoother electrical image signals which correspond to a size of imagedifferent from the original size; and (5) a variable magnificationcontrol means for controlling the first and second variablemagnification means so as to give image signals having a magnificationdesignated.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIG. 1 is a sectional view of an image reader;

FIG. 2 is a block diagram of an electric circuit of an image reader;

FIG. 3 is a flowchart of the main flow of the variation ofmagnification;

FIG. 4(a), (b) are flowcharts of the movement of a lens;

FIG. 5 is a flowchart of scan; and

FIG. 6 is a flowchart of the interrupt routine of the timer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment of the present invention, the optical variation ofmagnification will be adopted as far as a magnification to be set is inan allowable range wherein the magnification can be set optically. Ifthe magnification to be set is smaller than the allowable range, theoptical variation at a magnification of two times the magnification tobe set is combined with the optical variation at a magnification ofone-half of the magnification to be set. In general, the opticalvariation at a magnification of n (which is preferably a positiveinteger) times the magnification to be in the allowable range can becombined with the electrical variation at a magnification of an n-thtimes the magnification to be set. Further, the optical variation iscombined with an electrical variation at a fixed magnification (forexample, 1/1, 1/2, etc.) as needed.

Further, the dot density of a printer can be set in the embodiment ofthe present invention. Therefore, the output signal of the reading canbe sent to any printers having a variety of dot densities.

Referring now to the drawings, wherein like reference charactersdesignate corresponding parts through several views, an image reader ofan embodiment according to the present invention will be explained inthe following order:

(a) Image reader;

(b) Control of image reader;

(c) Main flow of reading at a variable magnification;

(d) Movement of lens; and

(e) Scan.

(a) Image reader:

FIG. 1 shows a schematical sectional view of an image reader accordingto the present invention. A light source for exposure illuminates adocument 6 placed on a glass platen 4. The light source of exposureconsists of a halogen lamp 2, a concave mirror 8 and a flat mirror 10.

The light reflected from the document 6 is reflected successively in ascan system or a slider which comprises a first mirror 12, a secondmirror 14 and a third mirror 16. Then, it is transmitted on aone-dimensional charge-coupled device (image sensor) 20 through anoptical lens assembly 18. The lens assembly is a zoom lens assemblywhich can vary the magnification of reading continuously.

The charge-coupled device (hereinafter referred to as "CCD") 20 is fixedto a CCD holder 22, which controls the position and the angle of the CCD20. The CCD holder 22 and the lens 18 are fixed on a carriage 24.

The reading size of an image of the document 6 can be variedcontinuously by moving the carriage 24 along the direction of the opticaxis of the lens 18 by using a motor M2 for the control ofmagnification.

The focusing can be controlled by moving CCD 20 along the direction ofthe optic axis by using a motor 26 fixed to the carriage 24.

As is well known, on scanning the document 6, the light source 2, 8, 10and the first mirror 12 are moved as one body in a direction of an arrowS at a velocity V, while the second and third mirrors 14, 16 are movedas one body in the direction of the arrow S at the velocity of (1/2)V,by using a scan motor M1 (not shown).

(b) Control of image reader:

FIG. 2 shows a block diagram of an electric circuit for the control ofthe image reader.

Various kinds of input and output signals are connected to amicroprocessor (hereinafter referred to as "CPU") 30. The followinginput signals are sent into CPU 30. A dot density signal is a signalwhich designates the resolution of a printer which is connected to theimage reader, and the signal corresponds, for example, to a dot densityof 240, 330 or 400 dots/inch. A magnification signal is a signal whichdesignates the magnification of reading of an image on the document 6. Astart signal is a signal which initiates the action of the reading. Theabove-mentioned input signals are sent from an operation panel (notshown). A lens position signal is generated when the lens 18 is locatedat an initial position where the magnification is one. A slider positionsignal is generated when the slider is located at a predeterminedstandard position. A document edge signal is generated when the slideris located at a position which corresponds to the leading edge of thedocument.

The scan motor M1, the lens motor M2 and the focusing motor 26 are allpulse motors, and they are driven by pulse-motor drivers 34, 36 and 38,respectively.

An exposure lamp signal is used for turning on the lamp 2.

An output signal of the image sensor 20 is transformed from an analogsignal to a digital one-bit signal by a binarization circuit 50, and thedigital signal is sent via an output circuit 40 to an external apparatus(printer) 14. The output circuit 40 sends or stops sending an outputsignal according to an output control signal received from CPU 30.

When the magnification of 1/2 is designated in the electrical variationof magnification a 1/2 signal of the output control signal is generated,and binary signals from the binarization circuit 40 are thinned out. Inother words, an odd-bit line of the binary signals is sent to a memory42 during a subscan in the longitudinal direction, while an even-bitline of the binary signals is sent via the output circuit 40 to aprinter 44 during a main scan in the transverse direction.

(c) Main flow of the reading at a variable magnification:

FIG. 3 shows a main flow of the reading at a variable magnification.When the source of electric power is turned on, the image reader isinitialized first (step P1). Next, the lens 18 is returned by the lensmotor M2 to the initial position at which the magnification is set toone (step P2), and the slider is returned by the scan motor M1 to thestandard position (step P3).

Then, it is decided whether the dot density is changed from theinitialized value or not (step P5). The dot density should be adaptedaccording to the specifications of a printer connected to the imagereader. If the dot density is changed, the lens 18 is moved by a lensmotor M2 to a new position (step P6), and the process returns to stepP5.

Next, it is decided whether the magnification is changed from theinitialized value, that is, one or not (step P7). If the magnificationis changed, the lens 18 and CCD 30 are moved to a new position (stepP6), and the process returns to step P5. The movement of the lens 18will be explained in detail in section (d); both changes in dot densityand in magnification are processed optically in a range wherein theoptical variation is allowed, otherwise the optical variation iscombined with the electrical variation.

Then, it is decided whether the start signal is received or not (stepP8). If the decision is no, the process returns to step P5. When thestart signal is received, a scan for reading the document starts (stepP9). The scan will be explained in detail in section (e). When the scanis finished, the process returns to step P5.

(d) Movement of lens:

The movement of lens 18 (step P6) will be explained in detail by using aflowchart shown in FIG. 4.

First, the real magnification of the image reader defined as themagnification times dot density/240 is calculated from the designatedmagnification and the dot density of the printer (step P10). In thisembodiment, the standard dot density is 240 dots/inch. Therefore, themagnifications of one at 240 and 480 dots/inch correspond to a realmagnification of one and two, respectively.

Next, it is decided whether the real magnification is in an allowablerange where the optical variation is allowed or not (step P12). If thedecision is yes, the 1/2 signal (output control signal) is not sent tothe output circuit 40 (step P14). If the real magnification is beyondthe allowable range, it is decided next whether the real magnificationis larger than one-half of the highest value of the allowable range(step P16). If the decision is yes, CPU 30 sends the 1/2 signal to theoutput circuit 40 (step P18), and the real magnification is set to ahalf value of the real magnification calculated (step P19). On the otherhand, if reduction to the designated magnification is impossible, aninstruction indicating that the magnification is to be changed isdisplayed on the operational panel (step P20), and the process returnsto the main flow.

Then, the lens position which corresponds to the real magnification iscalculated (step P22), and the distance of the movement of the lens 18is set as the difference between the present lens position and the newlens position calculated in step P22 (step P24). Next, it is decidedwhether the distance of the movement is positive or negative (step P26).If the distance is positive, the direction of the movement of the lens18 is set as an arrow CW shown in FIG. 1 (step P27). If the distance isnegative, the sign of the distance of the movement is set as positive(step P28), and the direction of the movement is set as an arrow CCW,shown in FIG. 1, which is the reverse direction of CW (step P29).

The lens motor M2 is a stepping motor, and the movement of the lens 18can be expressed in a unit of one step. For the driving of the lensmotor M2, the present phase is sent to the lens motor M2 (step P30).Next, the lens 18 is moved. After a prescribed time has passed (stepP32), a new phase is sent to the lens motor (step P34). Then, thedistance of movement is decreased by one (step P36), and it is decidedwhether the distance becomes zero or not (step P37). If the decision isno, the process returns to step P30, and the lens 18 will be movedfurther. If the movement of the calculated distance is finished, thelens motor M2 is stopped (step P38). Next, the focusing is controlled bymeans of the focusing motor 26 so that the difference between thedetected density of the black and white pattern of a standard pattern 28placed on the glass platen 6 becomes a maximum (step P39).

(e) Scan:

The scan of the reading (step P5) will be explained by using a flowchartshown in FIG. 5.

First, the direction of the movement of the scan motor M1 is set as CW,that is, scan direction (step P40). Next, the rate V of the scan MotorM1 is calculated for the real magnification (step P42), and thecalculated value is set in an interval timer so that timer interruptsare requested per required time interval (step P44). Then, the interruptis enabled (step P46). The timer interrupt will be explained later byusing FIG. 6.

Next, a scan starts. First, the exposure lamp 2 is turned on, and theexposure of a document starts (step P50). Then, the slider is moved bythe scan motor M1 until it reaches the lading edge of the document (stepP52). When the document edge signal is received (step P52), an outputcontrol signal is sent to the output circuit 40, and the output signalof the image sensor 20 begins to be sent to the printer (step P54).Next, it is decided whether a scan of the prescribed distance iscompleted or not (step P56). The prescribed distance has been set fromthe dot density and the magnification. When the scan is completed, theoutput control signal is stopped, so that the output signal of the imagesensor 20 to be sent to the printer is also stopped (step P58), and theexposure lamp 2 is turned off (step P59).

Then, the slider is returned as follows. The direction of movement ofthe slider is set as CCW, that is, the return direction (step P60), therate of M1 for the return is set (step P62), the interval timer is set(step P64), and the movement of the slider is started by the scan motorM1. The program waits until the slider returns to the standard position(step P66). After the slider returns to the standard position and theslider position signal is received by CPU 30, a timer interrupt isforbidden (step P68), the scan motor M1 is stopped (step P69), and theprocess returns to the main flow.

The timer interrupt on the drive of the scan motor M1 is explained byusing a flowchart shown in FIG. 6 as follows. When an interrupt by aninterval timer is requested between step P50 and step P68, the presentphase of the scan motor M1 is sent to the scan motor M1 (step P80).Then, the next phase for the next interrupt is set in the interrupttimer (step P82), where the next phase is determined according to thedirection of movement. Then, the process returns to the scan routine.

In the above-mentioned embodiment, the electrical variation ofmagnification is combined with the optical variation of magnificationwith the lens 18 if the required reduction of magnification is lowerthan the minimum value in the allowable range of the optical variation.

Similar to the above, it is also possible, according to the presentinvention, to combine the optical variation with the electricalvariation if such a high magnification larger than the maximum value inthe allowable range of the optical variation is designated.

This invention may be practiced or embodied in still other ways withoutdeparting from the spirit or essential character thereof. The preferredembodiments described herein are therefore illustrative and notrestrictive, the scope of the invention being indicated by the appendedclaims and all variations which come within the meaning of the claimsare intended to be embraced therein.

What is claim is:
 1. An apparatus for converting an optical image intoelectrical image signals with a magnification which is variable,comprising;an image sensor for transforming an optical image projectedthereon into analog image signals; a projection lens for projecting anoptical image onto the image sensor; optical magnification varying meansfor optically varying a size of the optical image to be projected on theimage sensor through the projection lens; converting means forconverting the analog image signals received from the image sensor intodigital image signals; electrical magnification varying means fortransforming the digital image signals received from the convertingmeans into other digital image signals so as to vary the magnification;and generating means for giving a magnification varying instruction,wherein the magnification inside a predetermined range is varied byoperating the optical magnification varying means in response to themagnification varying instruction while the magnification outside thepredetermined range is varied by operating the electrical magnificationvarying means in response to the magnification varying instruction. 2.An apparatus as claimed in claim 1, wherein said electricalmagnification varying means includes a memory storing the digital imagesignals received from the converting means.
 3. An apparatus as claimedin claim 1, further comprising focusing means for adjusting a focusingcondition of the optical image projected on the image sensor through theprojection lens.
 4. An apparatus for converting an optical image intoelectrical image signals with a magnification which is variable,comprising:an image sensor composed of a charge-coupled device fortransforming an optical image projected thereon into analog imagesignals; a projection lens for projecting an optical image onto theimage sensor; optical magnification varying means for optically andcontinuously varying a size of the optical image to be projected on theimage sensor through the projection lens; focusing means for adjusting afocusing condition of the optical image projected on the image sensorthrough the projection lens; converting means for converting the analogimage signals received from the image sensor into digital image signals;electrical magnification varying means for storing the digital imagesignals received from the converting means into a memory and generatingother digital image signals according to the digital image signalsstored in the memory so as to vary the magnification; and generatingmeans for giving a magnification varying instruction, wherein themagnification inside a predetermined range is varied by operating theoptical magnification varying means in response to the magnificationvarying instruction while the magnification outside the predeterminedrange is varied by operating the electrical magnification varying meansin response to the magnification varying instruction.